The present invention relates to a conveying arm for fitment to automatic wrapping machines by which products, in particular rolls of toilet tissue and kitchen paper, are packaged in multiples.
In automatic machines of the type in question (the art field to which the present application refers, albeit with no limitation implied), household paper products are assembled typically in packs of two or four and wrapped in clear plastic (see also Italian patent application IT BOA91 000409) by a succession of stations, the first consisting in an elevator on which the rolls are positioned in pairs, arranged in tangential contact with their respective axes parallel and horizontally disposed; the rolls are lifted in this same configuration by the elevator, moving upwards and into a first wrapping station beneath which a sheet of plastic film is extended in readiness to be fashioned into a wrapper.
This forcible upward movement results in the rolls being enveloped initially from the side uppermost, an operation that occurs with the assistance of a restraint afforded by at least one pair of vertical arms between which the rolls remain supported as the elevator descends in readiness for a further lift stroke. The successive stations are equipped with horizontal folders and/or bottom restraints by which the sheet of plastic film is caused to assume a configuration completely enveloping the rolls and with the two longitudinal edges overlapping.
In effect, the vertical arms are associated rigidly with and suspended thus from a pair of transversely disposed horizontal rails, of which the ends are in their turn associated rigidly with trolleys secured bilaterally, in pairs, to the looped chains of an endless conveyor; the distance between centers of the pairs of arms determines the space afforded to the rolls, whilst the chains advance by discrete steps in such a manner as to transfer the assembled packs through the various wrapping stations.
On completion of the folding steps, all of which effected along a predetermined feed path, the pack of rolls will pause at a station where the bottom overlapping edges of the film are sealed together.
There is a drawback encountered in such machines, namely, the time-consuming nature of the changeover from one production size of pack to another. This operation centers particularly on the arms by which the packs of rolls are gripped and conveyed through the work stations, since the pack must be supported stably between the arms as previously intimated; in effect, the single arms are adjustable for position by hand in relation to the chains, along an axis disposed at right angles to the feed path followed by the packs and afforded by the transverse rails, to which the pairs of arms are secured by fastening means of releasable embodiment.
The operation in question must therefore be carried out on a significant number of arms, each of which needing to be released, repositioned and secured in its turn. Naturally, the time required to complete such a procedure is not inconsiderable, and has a negative impact on the productivity of the machine overall.
Accordingly, the object of the present invention is to overcome the drawbacks mentioned above by the adoption of a conveying arm featuring economy and simplicity in construction, which can be fitted to and adjusted on the rails with speed and precision.